With continuing improvements in cost and performance, solid-state lasers have potential benefits as illumination components for display systems. Their inherent spectral purity, high brightness, and long operating life have sparked particular interest among designers of high-end color projection systems for digital cinema, simulation, and other high-performance imaging apparatus. However, proposed solutions for using laser light sources for digital projection fall short of what is needed for providing robust display apparatus that take advantage of this potential.
Stereoscopic projection has been one area of particular interest for cinema projection overall. Conventional configurations for stereo projection include configurations that use two projectors, one for the left eye and the other for the right eye. This basic model has been applied with earlier film-based systems as well as with digital projection equipment, from vendors such as Barco Corporation. Although such two-projector designs have successfully shown the feasibility and enhanced imaging capabilities afforded by stereoscopic imaging systems, these systems are expensive, require precision alignment to each other, and impose some additional requirements on theater design and layout that complicate retrofit installation.
Various types of solutions for stereoscopic projection have been presented for digital projector apparatus, including configurations that use only a single projector. These have typically included systems utilizing either of two types of spatial light modulators (SLMs). The first type of spatial light modulator used in proposed stereoscopic designs is the digital light processor (DLP), a digital micromirror device (DMD), developed by Texas Instruments, Inc., Dallas, Tex. The second type of SLM widely used for digital projection is based on liquid crystal technology, available both as a transmissive light modulator, the liquid crystal device (LCD), and as a reflective liquid crystal on silicon (LCOS) modulator.
Another type of light modulator solution for digital projection uses a linear light modulator that uses a one-dimensional array of n micro-devices and forms a two-dimensional image by forming m successive single-line images, each single-line image extending in a first direction, and then scanning these m successive line images in a direction orthogonal to the first direction in order to project an image of m×n pixels.
Among linear light modulators are grating light valve (GLV) designs, offered by silicon light machines as described in U.S. Pat. No. 6,215,579 (Bloom et al.) and others. Still other solutions have been proposed using grating electro-mechanical systems (GEMS) devices, such as those disclosed in commonly-assigned U.S. Pat. No. 6,802,613 (Agostinelli et al.).
With any type of stereoscopic projection system, some type of separation mechanism is needed in order to distinguish the left and right images that are combined on a common display screen, but are intended for the appropriate left and right eyes of the viewers. Left- and right-eye images can be separated in time, can be of different polarizations relatively orthogonal to each other, or can be of different wavelengths. Conventional two-projector systems can use any of these separation schemes as just described. Single-projector digital systems can also use any of these methods. However, because they must direct light from the same projection lens, single-projector systems inherently tend to be less efficient.
Time-sequencing systems use a “page flipping” technique. Page-flipping alternately displays left- and right-eye images to provide stereo images to one or more viewers wearing shutter glasses that are synchronized to the display refresh rates. One example of this type of display system adapted for presenting stereoscopic images to multiple viewers is given in U.S. Pat. No. 6,535,241 (McDowall et al.).
Stereoscopic systems using polarization differences provide the left- and right-eye images using light at respectively orthogonal polarizations. Viewers are provided with polarized glasses to separate these left- and right-eye images. One example of this type of display system using linearly polarized light is given in U.S. Pat. No. 7,204,592 (O'Donnell et al.). A stereoscopic display apparatus using left- and right-circular polarization is described in U.S. Pat. No. 7,180,554 (Divelbiss et al.).
Stereoscopic systems can separate left- and right-eye images by wavelength and provide viewers with filter glasses that are suitably designed to distinguish the appropriate image for each eye. One example of this type of spectral separation display system is given in U.S. Pat. No. 7,001,021 (Jorke).
One approach for stereoscopic imaging, outlined in U.S. Pat. No. 6,867,775 (Buck et al.) describes displaying an object for a plurality of viewers located in different positions, and generating separate stereoscopic images based on the position and image of the object representing the perspective view of the particular viewer. To generate the image that corresponds to each viewer, a plurality of spectral regions is filtered out of a radiation spectrum of an image display device. In order to produce different images that describe different position perspectives, different radiation or emission spectra of the image display device are decoupled as relatively narrow frequency bands, representing the three color receptors, for example. In order to separate the half images corresponding to each of the viewer's eyes, different adjacent spectral regions are preferably decoupled from the emission or radiation spectrum of the image display device. For a viewer A, for example, 445 to 455 nm, 515 to 525 nm, and 605 to 615 nm frequency bands, respectively, are decoupled for the left eye, and 460 to 470 nm, 530 to 540 nm, and 622 630 nm frequency bands, respectively, are decoupled for the right eye. For a viewer B, the frequency bands are shifted in comparable fashion and decoupled around the spectral lines at 480, 550, and 635 nm, respectively. In this way, two viewers A and B see different 3-D perspectives by using view glasses or other separators with different sets of filters. While this approach may provide different stereoscopic views of an object for individual viewers, however, it requires filter glasses that are highly selective and costly. Moreover, perfect spectral separation is not possible, so that there can be some crosstalk between viewers.
Recently, imaging apparatus have been adapted for use as dual-view systems, using technology and approaches similar to those applied to the task of stereoscopic imaging. Of considerable interest for gaming and simulation applications, dual-viewer operation is a variant of stereoscopic operation, provided using stereoscopic projection apparatus and techniques, with only a slight change at the viewer end. For dual-viewer mode, the change is straightforward: what had been termed the “left-eye image” for stereoscopic viewing is now presented to a first viewer and what had been termed the “right-eye image” is now presented to a second viewer. Similar techniques are used for separating the images presented to each viewer, using timing, polarization state, or wavelength.
Although the value of providing dual-view stereo viewing capability is recognized, conventional approaches for achieving this have proved less than satisfactory. For example, image crosstalk would be highly unfavorable for dual-view imaging. Approaches such as that outlined in the Buck et al. '775 disclosure do not have the capability to support dual-view stereoscopic imaging in which two viewers are presented with different image content and the image presentation for each viewer is stereoscopic. Other approaches struggle to provide sufficient brightness even with dual-view or stereoscopic imaging. For example, video multiplexing approaches, such at that shown in the McDowall et al. '241 disclosure, provide only ¼ the available light to each eye of the viewer during a single display cycle. Extending these approaches to the requirements of dual view stereoscopic imaging would not provide a satisfactory viewing experience.
Thus, it can be seen that there is a need for apparatus and methods for providing dual-view stereoscopic image display using linear modulator arrays.